The invention relates to an electrical liquid contact between a rotating annular member and an opposite, likewise annular member. These members define a central ring gap which is filled with a metallic liquid under pressure and which is bounded on each side by a lateral ring gap which extends radially or at an angle. Means are provided for sealing against the escape of the liquid at the sides of the central ring.
Such an electrical liquid contact, which is suited particularly for an electric unipolar machine with a horizontal shaft, is disclosed in Deutsche Auslegeschrift No. 1,246,102. In this known arrangement, circular ribs which are interleaved in the manner of a labyrinth seal are arranged to the sides of the liquid contact at the stationary member as well as at the rotating member. This is to prevent the metallic liquid from escaping laterally. However, labyrinth seals do contain a gap, so that, particularly at standstill, a part of the metallic liquid trickles out, especially since, with the very large diameters of the ring gas of the liquid contacts required for a unipolar machine of large power rating, considerable pressure differences between the members at the top and the bottom of the ring gap occur, which lead to an additional stress on the lateral seals. However, if the unipolar machine is to be used as a motor and is to be operated with varying speeds and directions of rotation, then the sealing of the ring gap against an escape of the liquid must be effective also if the machine is standing still.